AMD Dually
I honestly have no idea what this game is, but Im gonna investigate since its new and I might want to try it.
But, it sounds like your investing a good chunk of change in this PC... Id go for at least 2GB of good memory, and the newer AM2 boards allow for DDR2 (up to 1066 I believe). Dont skimp on the memory, as this chip has seen really good overclocking benchmarks compared to the older socket 939 and 940 variations. The memory is going to be the limiting factor when it comes to OC'ing. I have an older X2 3800+ and I love it, but Im running an Asus CrossFire board that only supports DDR. I think that due to the memory, I was only able to bump it up 400Mhz. This is still a considerable overclock, with very little heat increase (im using a Thermaltake Big Typhoon cpu cooler), but I think that with better memory it could have gone much higher.
Another thing to consider is SLI or XFire. If you want to get the most bang for the buck, Id go with one of these configurations. Im not going to say which is better because I havent checked out the market in quite some time, but whichever you choose, you can get one good video card now, and buy one to match it next year when its dirt cheap to expand the capability of the system and get more life out of it for a very low cost. If you choose to invest in this technology, it wont cost you very much up front compared to the single PCIe boards, but you will absolutely need a better PSU. I believe 500-550w rated PSUs are required for dual video cards.
So, at a minimum, get another 1GB stick of RAM, and if you want to make a more sound investment for a gaming rig, spend a little more and invest in either an SLI or CrossFire mobo and better PSU.
My 2c...